Microfluidic analyzers have been used to sense a plurality of analytes in whole blood, diluted blood, plasma or serum. Additionally in the rapidly growing fields of cell culture growth and fermentation, it is often necessary to measure glucose, glutamine, lactate, NH.sup.3, phosphate and iron in micro-scale fluid flow analysis systems.
Due to the scarce and often expensive nature of the fluid medium containing the analyte, it is imperative that the fluid medium should be conserved with only the smallest amounts used for the analysis. Also, the emphasis toward in-situ measurement of biological fluids such as cell culture media dictates that the analytical equipment should not only be small in size, but component parts of the analytical system should also be designed for easy removal from the system and rapid replacement of a new component part to the system so that cleanliness of the component can be accurately controlled without interruption in the monitoring effort. Moreover, such a component or assembly itself should be as free from contamination itself as possible.
There are several additional reasons why the measurement of sterile biological fluids benefit from the use of a disposable microfluidic; for the measurement of sterile fluids the measurement system should be enclosed, i.e. all wetted parts should be sealed so that they may be sterilized and remain that way during monitoring. If the entire fluidic system (including sensor, reagents and waste) is to be enclosed then economics dictate that it should be small, preferably very small.
Another aspect of the micro approach responds to the above-noted need to consume only small amounts of samples. If small amounts of sample are withdrawn for analysis then small conduits are needed to convey the sample to the analyzer in order to deliver a timely result. This can be accomplished in two ways: first the conduit should be small in diameter, secondly it should be as short as possible. The best way to keep the sample conduit short is to move the analyzer to the sample. The only practical way to accomplish this is to develop the analyzer and conduit on a micro scale.